Production of continuous filament,non-woven webs

ABSTRACT

A method for the production of continuous filament, non-woven webs, comprising directing downwardly towards a moving receiving surface at least two curtains of continuous diverging filaments, in which the filaments are separated and substantially uniformly distributed across each curtain, influencing the direction of movement of the filaments of each curtain so that they cease to diverge and become substantially parallel in the vicinity of the receiving surface, the filamentary curtains being arranged in such a manner that neighboring edges of the filamentary curtains are in contact at the receiving surface, overfeeding the filamentary curtains onto the receiving surface to form a unitary non-woven web having a width dimension which is substantially equal to the sum of the widths of the webs which would be formed by the individual filamentary curtains and subjecting the unitary non-woven web to a heat bonding process to bond together the filaments.

United States Patent US. Cl. 156-181 1 Claim ABSTRACT OF THE DISCLOSUREA method for the production of continuous filament, non-woven webs,comprising directing downwardly towards a moving receiving surface atleast two curtains of continuous diverging filaments, in which thefilaments are separated and substantially uniformly distributed acrosseach curtain, influencing the direction of movement of the filaments ofeach curtain so that they cease to diverge and become substantiallyparallel in the vicinity of the receiving surface, the filamentarycurtains being arranged in such a manner that neighbouring edges of thefilamentary curtains are in contact at the receiving surface,overfeeding the filamentary curtains onto the receiving surface to forma unitary non-woven web having a width dimension which is substantiallyequal to the sum of the widths of the webs which would be formed by theindividual filamentary curtains and subjecting the unitary non-woven webto a heat bonding process to bond together the filaments.

The present invention relates to the production of continuous filament,non-woven webs.

The width of a non-woven web is an important factor to be consideredduring its manufacture since the width of the web is to a large extentdictated by the nature of its intended end-use. However, the width towhich a continuous filament, non-woven web can be made is limited by thedesign and dimenisons of the apparatus used to spray or lay thefilaments into the form of a web.

Accordingly, in order to obtain wider webs, two or more webs may bejoined together as, for example, by bonding or stitching, to produce aunitary web having the desired increased width. This procedure is onlypossible, however, when the intended end-use of the unitary web does notrequire the web to have continuous, uniform physical properties acrossits width, since the or each joint will exhibit different physicalproperties from the remainder of the unitary web.

Also, in order to obtain wider webs, use has been made of processes inwhich one or more sprays of continuous filaments are traversed across amoving receiving surface to build up a web having a width which isgreater than would normally be produced if the sprays of continuousfilaments were not traversed. In such processes, the filaments areusually forwarded to the receiving surface in the form of a diverging,conical spray, and as a result the web tends to have large marginalportions which taper, that is they decrease in thickness, towards theedges of the web. Excessive trimming of the marginal portions of the webis then needed to obtain a product having uniform thickness. Thetraverse movements of the or each filamentary spray causes long lengthsof individual filaments to cover the surface of the web withoutintermingling with other filaments, such that after bonding of thefilaments in the web the non-intermingled filament lengths may easily betorn away from the web surface. Further disadvantages of such processesare the restric- "ice tion of the web forwarding speed impose-d by thelimitations of traversing the spraying apparatus at suitablefrequencies, and the necessity for the design and control of thetraversing pattern in order to achive thickness uniformity in the web.

According to the present invention, a method for the production ofcotninuous filament, non-woven webs, comprises directing downwardlytowards a moving receiving surface at least two diverging curtains ofcontinuous filaments, in which the filaments are separated andsubstantially uniformly distributed across each curtain, influencing thedirection of movement of the filaments of each curtain, so that theycease to diverge and become sub stantially parallel in the vicinity ofthe receiving surface, the filamentary curtains arranged in such amanner that neighbouring edges of the filamentary curtains are incontact at the receiving surface, and overfeeding the filamentarycurtains onto the receiving surface to form a unitary non-woven webhaving a width dimension which is substantially equal to the sum of thewidths of the webs which would be formed by the individual filamentarycurtains.

By o verfeeding is meant that the speed at which the filaments traveltowards the receiving surface is greater than the speed at which the webis taken away thereon.

The preferred contact occurs when the filaments in the neighbouringedges of the filamentary curtains are relatively positioned as areadjacent filaments in an individual curtain, so that they are laid downand intermingled on the receiving surface in a similar manner, with theresult that the joining line of adjacent curtains is not visible in theweb, and, after bonding thereof, is not detectable by tests foruniformity of thickness and tensile properties. However, a small amountof overlap between the edges of the filamentary curtains may betolerated so long as this amount does not result in the web havingobjectional physical discontinuities therein.

A convenient method of producing a curtain of continuous filaments isthat .described in copending (US. Ser. No. 605,351), wherein a bundle ofcontinuous filaments is formed into a substantially uniform ribbon offilaments by passing the bundle through a gas-operated banding deviceand the ribbon of filaments is passed through a gas-operated spreadingdevice and issues therefrom as a diverging curtain of filaments. For thepurpose of the present invention, this prior method is at leastduplicated by arranging at least two sets of the curtainproducirrgapparatus in side-by-side arrangement.

One method of achieving the parallel arrangement of the filaments in theviciinty of the receiving surface is to position the gas-operatedspreading devices at a height above the receiving surface suflicient toensure that the effect of the exhaust gases from the spreading devicesis so diminished that the gravitational forces on the filaments becomesthe dominant influence. Another method involves the use of suitablypositioned deflector plates which serve to redirect the exhaust gasesfrom the spreading devices to impinge on the diverging filaments wherebythey become substantially parallel under the influence of the redirectedexhaust gases.

A preferred embodiment of the invention will now be described by way ofexample:

Two separate bundles of thermoplastic, synthetic, continuous filaments,each bundle containing 112 filaments,

were formed into two ribbons, each of inch width,

The spreading devices, which provided sufiicient tension on thefilamentary ribbons to remove them from the rolls, also spread thefilaments into two side-by-side filamentary curtains and forwarded thediverging curtains, initially entrained in high velocity air issuingfrom the spreading devices, towards an air-permeable conveyor surfacehaving a width of 14 inches and moving at 15 feet per minute. Thearcuate slot of each spreading device had a radius of 9 /2 inches, a gapof 0.012 inch, and was supplied With air under a pressure of 8 poundsper square inch. The distance from the slot of each spreading device tothe conveyor surface was 26 inches. The filaments were forwarded fromeach spreading device at a speed of 4000 feet per minute and wereoverfed onto the conveyor surface.

It was found that, while the filaments issuing from each spreadingdevice were formed into a diverging filamentary curtain in which thefilaments were separated and substantially uniformly distributed acrossthe curtain, the filaments of the curtain ceased to diverge as theyapproached the conveyor surface and became less influenced by the highvelocity air issuing from the spreading device. As a result thefilaments became substantially parallel due to the action of gravity.

The spreading devices were adjusted so that the centre of eachfilamentary curtain was positioned at a point 2% inches from, and on theappropriate side of, the longitudinal axis or centre line of theconveyor surface. The filamentary curtains were then adjusted, each toan effective width of /2 inches, so as to merge the neighbouring edgesof the curtains on the centre line of the conveyor and form a non-Wovenweb having an effective width of 11 inches.

The web was then passed through a hot calendering process to bond thefilaments, whereafter no visible joining line of the curtains formingthe web could be detected. Subsequent tests for thickness uniformity andtensile properties also failed to detect the joining line.

Making non-woven webs according to the method of the invention has theadvantages over the known processes in that no undue limitation in theweb forwarding speed on the conveyor surface is imposed and lesstrimming of the web is required since the tapering marginal portions 4of the web are not present to the extent of those found intraversed-filament webs.

What I claim is:

1. A method for the production of continuous filament, non-woven webs,comprising directing downwardly towards a moving receiving surface atleast two curtains of continuous diverging filaments, in which thefilaments are separated and substantially uniformly distributed acrosseach curtain, influencing the direction of movement of the filaments ofeach curtain so that they cease to diverge and become substantiallyparallel in the viciinty of the receiving surface, the filamentarycurtains being arranged in such a manner that neighbouring edges of thefilamentary curtains are in contact at the receiving surface,overfeeding the filamentary curtains onto the receiving surface to forma unitary non-woven web having a width dimension which is substantiallyequal to the sum of the widths of the webs which would be formed by theindividual filamentary curtains and subjecting the unitary non-woven webto a heat bonding process to bond together the filaments.

References Cited UNITED STATES PATENTS 2,413,551 12/1946 Englund156----167 2,736,676 2/1956 Frickert 156167 3,288,582 11/1966 Wong etal. 156---167 3,341,394 9/1967 Kinney 156-167 3,436,797 4/ 1969 Graf eta1. 156167 3,442,751 5/1969 Langlois 156167 2,900,700 8/1959 Frickert156181 2,577,214 12/1951 Slayter 156181 FOREIGN PATENTS 1,246,39812/1959 France 156-167 787,872 6/1968 Canada 156-166 470,675 9/1937Great Britain 156 166 BENJAMIN R. PADGE'IT, Primary Examiner B. H. HUNT,Assistant Examiner US. Cl. X.R.

